1. Field of the Invention
This invention relates to improved designs for rotary drill bits having removable nozzles for air or other drilling fluid and more particularly to a means for retaining said fluid nozzle in place.
2. Brief Description of the Prior Art
The placement of one or more passageways in a rotary drilling bit to conduct air or other drilling fluids from the central bore of the bit to the rotating cutters is well known. The drilling fluid thus directed serves to cool the cutters and to carry cuttings away from the cutters. However, the presence of these passageways makes it possible for cuttings and other foreign materials to enter the interior of the bit when the circulation of the drilling fluid ceases and thus to impair the further operation of the bit. This problem has been dealt with by placing check valves or filters in the interior bore passageways of rotary drill bits. For example, Nickles U.S. Pat. No. 3,198,269 discloses a single passageway leading from the interior bore of the bit to the space directly above the rotary cutters. A spring loaded check valve is placed in the interior bore and in the single passageway and serves as a nozzle to direct drilling fluid between the cutters and also serves to prevent reverse flow through the passageway into the interior bore. The check valve is removable through the top of the bit when it is disconnected from the drill string.
The check valve assembly in the drill bit disclosed in the Nickles patent is removable from the bit only through the top thereof, thus necessitating the detachment of the drill bit from the drill string in order to remove the check valve assembly. Furthermore, the Nickles bit provides for only one passageway to direct drilling fluid between the bits and thus does not permit the application of a stream of drilling fluid at multiple points on the cutter. In applicant's prior U.S. Pat. No. 3,685,601, there is disclosed an improvement in drill bits in which there are provided a plurality of passageways for discharging air or other drilling fluid between the cutters and each passageway having a nozzle or check valve assembly removably positioned therein. In this construction, the nozzle or check valve is removably secured in place by means of a set screw. There is some disadvantage to the use of a set screw in this arrangement since the set screw may come loose during operation and allow the air nozzle or check valve assembly to fall out.
Moore U.S. Pat. No. 3,744,581 discloses a different type of fluid nozzle for roller cutter drill bits which is removably positioned and secured by a check valve and sealed by a peripheral 0-ring. The use of a set screw in this type of nozzle is subject to the same disadvantage mentioned above.
Scarborough U.S. Pat. No. 3,084,751 discloses an air nozzle for rotary cutter drill bits which is held in place by a thick wire having a head somewhat like a nail for ease of removal. The retaining wire or rod is inserted into matching grooves in the outside of the nozzle member and the inside of the passageway in which the nozzle member is fitted. This arrangement has the slight disadvantage that it is necessary to have an extra groove machined or cut in the passageway in which the nozzle is positioned. This cutting or machining operation adds to the expense of manufacture of the drill bit.
Mori U.S. Pat. No. 3,220,754 discloses a removable air or other drilling fluid nozzle in a drag type bit. The nozzle is constructed similarly to that of Scarborough and is held in place by a retaining rod inserted into a groove cut on only one side of the nozzle and aligned with a matching groove in the passageway in which the nozzle is fitted. This arrangement is complicated to manufacture and is difficult both in assembly and in disassembly.